Central effects of ghrelin on serum growth hormone and morphology of pituitary somatotropes in rats

Ghrelin, an endogenous ligand for the growth hormone (GH) secretagogue receptor, was originally purified from rat stomach; subsequently, ghrelin neurons were found in the arcuate nuclei of rats. Central effects of the peptide on GH release, however, remain to be clarified. The aim of the present study was to determine the morphologic features of GH-producing pituicytes and serum GH concentration after central administration of ghrelin. Five injections of rat ghrelin or phosphate-buffered saline (PBS; n = 10 rats/group) were given every 24 hrs (1 microg of ghrelin in 5 microl of PBS) into the lateral cerebral ventricle of male rats. Significant (P < 0.05) increases in absolute and relative pituitary weights occurred in ghrelin-treated rats versus controls (58% and 41%, respectively). Morphometric parameters (i.e., the volume of GH cells, volume of their nuclei, and volume density) all significantly (P < 0.05) increased by 17%, 18%, and 19%, respectively, in the ghrelin-treated group versus controls. Terminal serum concentration of GH was significantly (P < 0.05) increased by 15% with ghrelin treatment. The results clearly document that daily nanomolar doses of ghrelin into the lateral cerebral ventricle stimulate GH cell proliferation and promote GH release. Thus, achieving pharmacologic control of central ghrelin receptors is a promising modality to modulate the actions of GH.     

Partial growth hormone deficiency with pituitary stalk transection.

Partial growth hormone deficiency was found in a 13-year-old Japanese boy who was born by breech delivery. Magnetic resonance imaging showed transection of the pituitary stalk and the presence of an ectopic posterior lobe located at the proximal stump of the transected stalk.     

Autosomal-dominant isolated growth hormone deficiency (IGHD type II) with normal GH-1 gene

BACKGROUND: Autosomal-dominant isolated GH deficiency (IGHD) is a rare disorder that is commonly believed to be due to heterozygous mutations in the GH-1 gene (GH-1). These mutations cause the production of a protein that affects the release of the product of the normal allele. Rarely, heterozygous mutations in the gene encoding for HESX-1 gene (HESX-1) may cause autosomal-dominant IGHD, with penetrance that has been shown to be variable in both humans and mice. SUBJECTS AND METHODS: We have sequenced the whole GH-1 in the index cases of 30 families with autosomal-dominant IGHD. In all the families other possible causes of GH deficiency and other pituitary hormones deficits were excluded. We here describe the clinical, biochemical and radiological picture of the families without GH-1 mutations. In these families, we also sequenced the HESX-1. RESULTS: The index cases of the five families with autosomal-dominant IGHD had normal GH-1, including the intronic sequences. They had no HESX-1 mutations. CONCLUSION: This study shows that GH-1 mutations are absent in 5/30 (16.6%) of the families with autosomal-dominant IGHD and raises the possibility that mutations in other gene(s) may be involved in IGHD with this mode of transmission.     

A case of Silver-Russell syndrome (SRS): multiple pituitary hormone deficiency,lack of H19 hypomethylation and favourable growth hormone (GH) treatment response

Hypomethylation of the imprinting control region 1 (ICR1) at the IGF2/H19 locus on 11p15 is linked to Silver-Russell syndrome (SRS) and/or hemihypertrophy. This SRS patient was born in term with weight of 3500 g (50 percentile) and length 48 cm (>1 SD below the mean). He was first noticed at the age of 10 years for short stature (114.5 cm, −3.85 SD), relatively normal head circumference, a classic facial phenotype, hemihypertrophy (2.5 cm thinner left arm and leg in comparison to the right, asymmetric face), moderate clinodactyly and striking thinness (BMI of 15.3). At the age of 30, the body asymmetry ameliorated (1 cm thinner left arm and leg than the right), and BMI normalized (20.5 cm). Methylation analysis was performed by bisulphate treatment of DNA samples, radiolabelled PCR amplification, and digestion of the PCR products using restriction enzymes. The patient had normomethylation, and in addition hypopituitarism, with low levels of growth hormone (GH) (provocative testing before the start and after termination of GH treatment), thyroxin, TSH, FSH, LH and testosterone. The GH was given for six years, growth response was satisfactory and he reached an adult height of 166 cm. This is a first report of hypopituitarism in a patient with SRS without H19 hypomethylation. It seems that the lack of hypomethylation in this hypopituitary SRS patient is responsible, at least partly, for the favourable final adult height under GH treatment.     

Genetic and molecular analysis of familial isolated growth hormone deficiency

Familial isolated growth hormone deficiency (IGHD) has been associated with complete deletions of the hGH-N gene encoding the pituitary growth hormone (GH) in a large number of cases. However, there is still no alternative empirical explanation for the remaining familial or non-familial IGHD cases. We studied a large kindred including five IGHD-affected first cousins to determine possible IGHD inheritance and whether the hGH-N gene was the cause of IGHD in this pedigree. Sex-linked and autosomal recessive transmission of IGHD in this kindred was rejected. Autosomal dominant inheritance was the most probable explanation according to a model of one locus with two alleles, one being dominant for IGHD, under genetic modifiers or epistasis. Southern blotting analysis (BamHI and HindIII digestions) was used to determine whether the hGH-N gene was present in the patients and their family members. Because we found that the hGH-N gene was present, five restriction fragment length polymorphisms (RFLPs; HincII, MspI-A and B, and BglII-A and B) linked to the hGH-N gene were used to try to identify the possible RFLP haplotypes in the pedigree that could be markers or associated with the abnormal hGH-N alleles responsible for IGHD. From the haplotype analysis, it appeared that other genes not linked to the hGH-N gene cluster were the cause of the IGHD phenotype in this kindred. An alternative conclusion could be that the hGH-N gene was responsible for IGHD in this kindred, if a mutation (gene conversion) at the MspI-B site or a reciprocal recombination event between the HincII and MspI-B sites occurred from generation P to F1 and a similar event took place from generation F1 to F2. The non-significant GH responses of patients to the growth releasing factor test confirmed that the hGH-N gene structural product or some step in its regulation was responsible for causing IGHD in this kindred. We suggest that genetic micromutations in the hGH-N gene are present and are responsible for IGHD. We developed a method using the polymerase chain reaction to amplify a 790-bp fragment of the hGH-N gene. The fragment spanned from the second part of the dyad symmetry region in the non-transcribed 5 end of the hGH-N gene to 9 bp before the alternative splice-acceptor site in exon 3. The expected fragment was verified by its digestion with seven diagnostic resctriction endonucleases (BamHI, FspI, PstI, NdeI, BssHII, BglII and HincII). The results showed no deletions or insertions greater than 35 bp in the hGH-N amplified fragment from the DNAs of the IGHD patients and their family members.Presented, in part, at the VIth International Congress of Auxology, Madrid, Spain, 15–19 September 1991.     

Isolated thyrotropin deficiency due to a pituitary tumour.

Hypothyroidism due to isolated deficiency of thyrotropin (TSH) associated with an enlarged sella turcica, presumably the result of a nonfunctioning pituitary adenoma, occurred in a 58-year-old man. Low serum concentrations of TSH and thyroid hormones, together with the lack of TSH response to administration of thyroid releasing hormone, indicated a pituitary deficiency of TSH. Serum values of other pituitary hormones were normal.     

Repetitive injections of growth hormone releasing hormone (GHRH1-44) to normal volunteers and patients with growth hormone deficiency

The present study was designed to answer the following three questions: Is there any difference between the growth hormone (GH) response to i.v. injections of GHRH 1-44 by a slowly injecting hormone pump or to a s. s. or rapid i. v. injection by syringe? Do nocturnal injections of GHRH 1-44 i. v. elicit different GH levels than during daytime? Can repetitive administration of GHRH 1-44 in patient with GH deficiency induce a physiological GH pattern and thereby normalize the condition resulting from a hypothalamic defect? A rapid i. v. bolus injection of 50 micrograms GHRH 1-44 by syringe with an injection time of one second elicited in the same subject at the same time of the day a twofold greater response than a slowly injecting (60 seconds) hormone pump. In six male adult volunteers each GHRH i. v. bolus was followed by a GH secretory pulse. The GH response at night (area under the curve and peak plasma GH levels) was significantly greater than at daytime (P less than 0.05) and greater than the GH pulses measured during a spontaneous nocturnal profile (P less than 0.05). Out of six GH deficient young adult patients who had been receiving extractive GH until two years prior to the study, three responded much like the controls, the other three patients-those who lacked any spontaneous nocturnal GH peaks-had markedly lower GH levels after GHRH (P less than 0.05). However, there was a clear-cut GH release after GHRH injection in each patient.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth hormone and IGF-I modulate local cerebral glucose utilization and ATP levels in a model of adult-onset growth hormone deficiency

Decreases in plasma IGF-I levels that occur with age have been hypothesized to contribute to the genesis of brain aging. However, support for this hypothesis would be strengthened by evidence that growth hormone (GH)/IGF-I deficiency in young animals produces a phenotype similar to that found in aged animals. As a result, we developed a unique model of adult-onset GH/IGF-I deficiency by using dwarf rats specifically deficient in GH and IGF-I. The deficiency in plasma IGF-I is similar to that observed with age (e.g., 50% decrease), and replacement of GH restores levels of IGF-I to that found in young animals with normal GH levels. The present study employs this model to investigate the effects of circulating GH and IGF-I on local cerebral glucose utilization (LCGU). Analysis of LCGU indicated that GH/IGF-I-deficient animals exhibit a 29% decrease in glucose metabolism in many brain regions, especially those involved in hippocampally dependent processes of learning and memory. Similarly, a high correlation between plasma IGF-I levels and glucose metabolism was found in these areas. The deficiency in LCGU was not associated with alterations in GLUT1, GLUT3, or hexokinase activity. A 15% decrease in ATP levels was also found in hippocampus of GH-deficient animals, providing compelling data that circulating GH and IGF-I have significant effects on the regulation of glucose utilization and energy metabolism in the brain. Furthermore, our results provide important data to support the conclusion that deficiencies in circulating GH/IGF-I contribute to the genesis of brain aging.     

Dosing of growth hormone in growth hormone deficiency

Growth hormone (GH) treatment of GH-deficient (GHD) children is to a certain extent standardized worldwide. Recombinant 22 kDa GH is injected once daily by the subcutaneous route, mostly in the evening. The amount of GH injected (calculated per kg body weight or body surface area, expressed in terms of IU or mg) in prepubertal children mimics the known production rate (approximately 0.02 mg [0. 06 IU]/kg body weight per day). However, there is a wide variation in dosage, the reasons for which are partly unknown and partly due to national traditions and regimes imposed by authorities regulating reimbursement. The situation during puberty is less standardized, with most clinicians still not increasing the dosage according to known production rates. The results of these approaches in terms of adult height outcome are not always satisfactory. In order to achieve optimal height development during childhood, puberty and adulthood, strategies must be developed to individualize GH dosing according to set therapeutical goals taking into account efficacy, safety and cost. The implementation of prediction algorithms will help us to reach these goals. In addition, other response variables will have to be monitored during treatment in order to correct for deficits resulting from GHD.     

A case of pituitary adenoma producing both growth hormone (GH) and adrenocorticotropic hormone (ACTH).

The authors report a very rare case of pituitary adenoma producing both GH and ACTH. A 29-year-old female was admitted with obesity, amenorrhea, acromegaly, hirsutism, excessive pigmentation, acne, and diabetes mellitus. Computed tomography revealed an intrasellar tumor 16 mm in height, with a destroyed sellar floor. The blood concentrations of GH, ACTH and cortisol were increased (GH: 92 ng/ml, ACTH: 94 pg/ml, cortisol: 18.3 micrograms/dl). No diurnal variation in the amount of cortisol was observed. The urinary 17-OHCS was suppressed by 8 mg but not by 2 mg of dexamethasone. A subtotal adenomectomy was then performed through the transsphenoidal approach, which led to a sufficient reduction of both blood GH and ACTH (cortisol). Histologically the tumor was an acidophilic pituitary adenoma. Immunoperoxidase staining showed diffuse GH and sporadic ACTH producing cells, but failed to show any cells producing both hormones. The electron micrograms of neoplastic cells showed the ultrastructural characteristics of respective GH and ACTH cells. Another increase in both GH and cortisol, which occurred 19 months after the operation, has been controlled by bromocriptine administration. This case may be the first reported case of a pituitary adenoma producing both GH and ACTH, not accompanied by prolactin (PRL) hypersecretion, which has been fully confirmed endocrinologically and histopathologically.     

Distortion of cyclic AMP responses to catecholamine due to destruction of the hormone.

The acute actions of low and moderate concentrations of catecholamines on cyclic AMP metabolism in SV40-transformed human lung fibroblasts (VA13) were seriously distorted by non-enzymatic destruction of the agonist. Catecholamine destruction, as measured directly with an isotopic method, was slowed by a variety of anti-oxidants and chelating agents. A combination of two anti-oxidants, ascorbate and thiourea, was very effective in protecting isoproterenol in the cell culture system. That is, there was a 10-fold increase in the sensitivity of VA13 to isoproterenol and the duration of action of the catecholamine was greatly prolonged. However, the anti-oxidants did not alter the responses of the cells to prostaglandins. We conclude that any quantitative studies of cyclic AMP responses to catecholamines must address the question of agonist destruction if meaningful results are to be expected. The use of anti-oxidants, especially the combination of ascorbate and thiourea, would appear to be advisable, particularly in situations where the catecholamine concentrations are less than supramaximal.